Electrical receptacle with safety closure



March 20, 1951 c. T. VON HOLTZ ELECTRICAL RECEPTACLE WITH SAFETY CLOSURE Filed Oct. 15, 1948 2 Sheets-Sheet 1 INVENTOR s 2% ML BY W M M 094mm;

ATTORNEY;

March 1951 c. T. VON HOLTZ' ELECTRICAL RECEPTACLE WITH SAFETY CLQSURE Filed Oct. 15, 1948 2 Sheets-Sheet 2 Patented Mar. 20, 1951 ELECTRICAL RECEPTACLE WITH SAFETY CLOSURE Charles '1. Von Holtz, Bridgeport, Conn., assignor to Harvey Hubbell, Inc., Bridgeport, Conn., a corporation of Connecticut Application October 15, 1948, Serial No. 54,604

8 Claims.

This invention relates to electrical receptacles, which include terminals concealed within the body of the receptacle and engageable by the prongs of a plug inserted into passages in the receptacle for the purpose of making a connection between conductors connected, respectively, to the terminals and the prongs. More particularly, the invention is concerned with a novel receptacle of the safety type, which includes means for preventing contact with a single terminal only of the receptacle, as by the insertion of a tool or other article through one passage. The safety means of the new receptacle also act to suppress the arc that may develop when a heavy current flow is broken by disengagement of the plug prongs from terminals.

The new receptacle is superior to prior sim ilar safety receptacles in that it may be employed with any standard type of plug and the prongs of the plug may be inserted in the passages to make a connection by a single straight line movement. Also, the safety means of the receptacle are made up of a relatively few parts, of which the principal ones are duplicates and can be readily produced at little expense by molding operations. Because of its simplicity, the receptacle can be easily assembled and the manufacturing cost is relatively low.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which Fig. l is a fragmentary longitudinal sectional View on the line l| of Fig. 2, showing one form of a receptacle embodying the invention;

Fig. 2 is a fragmentary sectional view on the line 2-2 of Fig. 1;

Figs. 3 and 4 are fragmentary sectional views on the lines 33 and 4-4, respectively, of Fig. 2;-

Fig. 5 is a view similar to Fig. 4 showing a plug with its prongs inserted into the receptacle;

Fig. 6 is a sectional view on the line 66 of Fig. 7, showing the safety means with the prongs of a plug inserted;

Fig. '7 is a sectional view on the line l-J of Fig. 6;

Fig. 8 is a view similar to Fig. 3, showing a plug with its prongs inserted;

Fig. 9 is an expanded perspective view showing the parts of the safety means;

Fig. 10 is a perspective view showing the parts of the safety means in the positions which they occupy, when the prongs of a plug have been inserted into the receptacle; Y

Fig. 11 is a view similar to Fig. 4 of a modified construction;

Fig. 12 is a view similar to Fig. 11, showing the prongs of a plug inserted into the receptacle;

Fig. 13 is a View in perspective of a part employed in the modified receptacle;

Fig. 14 is a sectional view on the line lfill l of Fig. 13;

Fig. 15 is an end view on the line l5-I5 of Fig. 16 of one of the parts used in the modified construction; and

Fig. 16 is a plan view of the part shown in Fig. 15.

The new receptacle. in the form shown in Fig. 1 includes a pair of complementary housing members 2B, 21 secured together in any suitable manner and made of insulating material. The opposed faces of the housing members are holloweo. out to form a chamber 22 and a pair of spring terminals 23 are mounted on the end wall of the member 29 within the chamber 22 by means of screws 24. In the use of the receptacle, the ends of conductors 25, usually within a fibrous covering 26, are passed through an opening in the housing member 2%.; and connected electrically to the respective terminals 23.

The housing member 2? is provided with a pair of passages 21 aligned with the terminals, so that the prongs 28 of a plug 29 may be inserted through the passages to engage the terminals. The inner end of housing member 23 is hollowed out to form a chamber 3d containing the safety means, which are confined within the chamber by a removable plate secured by screws 3 la to the end wall of member 2i within chamber 22, although, if desired, chamber 39 may be closed by an extension on housing member 20. The safety means thus lie between an inner wall 32 formed, in the construction shown, by part of plate 3|, and an outer wall 33, which is part of the outer end of housing member 2 I.

The safety means comprise a pairof identical door members 34, which are of insulating material and may be made of a suitable plastic by a molding operation. Each door member includes a base 35, from one side of which a short leg 36 and a long leg 3! extend at opposite ends thereof. Between the legs and spaced therefrom, the base is provided with a stud 38, on which the end of a coiled compression and torsion spring 39 may be mounted. The short leg of each door element is formed with a ledge against which an end 38a of the torsion spring bears. Each base is formed with a cam surface 4|, which extends lengthwise of the base along one edge thereof.

Each element is so formed as to make contact with the outer wall 33 of the chamber as over an extended area and to make contact with the wall 32 of that chamber over a limited area. For this purpose, the surfaces of the outer sides of the base and the legs of each element lie substantially in a plane, while the inner surface of the base is provided with a projection 52, which lies at the end of the base, from which the long leg projects, and extends parallel to that leg. In the construction shown, the rear surface 6-3 of the base lies substantially in a plane which, if extended, would intersect the plane of the front faces of the base and legs, so that the thick end of the base may be considered to form the projection, which makes a line contact with the inner surface of wall 32. The torsion spring 39 is so formed that, in the assembled condition of the safety means, the spring urges the door elements apart and the ends of their bases lie within passages 2? with the cam surfaces t! on the elements accessible through the outer ends of the passages. The spring also tends to hold the elements in the normal positions described, that is, with each element making extended contact with. the inner surface of wall 33 and a limited contact at the end of its projection 52 with the inner surface of wall 32. In this relation of the parts, the end of the long leg of each element is aligned with the short leg of the other element and the passages are closed by the sides of the bases of the elements, on which the cam surfaces are formed.

When the prongs of a plug are inserted into the outer ends of passages 27 and moved inwardly to engage the cam surfaces ll on the door elements, each element is initially rocked on its projection d2 against the resistance of spring 39, until the end of the rear surface of the base of the element remote from its projection 12 engages the inner surface of wall 32. In this movement of each element, its long leg remains in about its initial position, while the short leg moves inwardly so as to lie out of alignment with the long leg of the other element. On further inward movement of the prongs, they act on cam surfaces ti to force the elements toward one another against the action of spring 39, and such movement is permitted, because the long leg of each element is no longer aligned with the short leg of the other and can slip by that short leg. As the inward movement of the prongs continues, the door elements are finally forced into chamber 36 a sufficient distance to permit the prongs to pass by the elements and engage terminals 23. When the plug is removed and the door elements are freed thereby, spring 39 restores the elements to their normal positions, in which the cam surface on each element extends across its passage 2i, and the outer surfaces of the elements have extended contact with wall 33 and the elements engage wall 32 only at the ends of their projections 12.

If an attempt is made to insert an article, such as the end of a screw driver or a piece of wire, into one of the passages 27, the article will engage the cam surface of the door element closing that passage and will cause the element to rock on its projection t2 and make extended contact with wall 32. However, the rocking movement of only one of the elements does not move its long leg out of alignment with the short leg of the element which has not been rocked. The alignment of the legs referred to therefore prevents the element rocked by the article from being forced into chamber 36. The element will, therefore, continue to close its passage 2i and t the article can, therefore, not be forced through the passage into contact with a terminal In the construction above described, the inner surface of each wall is flat and, in order to provide for the desired rocking movenent of the door elements relative to that wall, the rear surface of each element is formed with a projection. If desired, the door elements may be formed with flat parallel front and rear surfaces and the limited contact of each door element with the inner wall of chamber 39 may be obtained by proper formation of the inner surface of that wall. In such a modified construction, the plate 3!, corresponding to plate 3 i, is formed with spaced offset transverse projections which are thicker at one end than at the other. When the plate is mounted in place in housing element 2!, the projections extend into chambe Eli and, in the normal position of the door elements, their front surfaces lie in full contact with the outer wall 33 of chamber 39 and the rear surface of each element engages a projection with an approximately line contact. The spring 3% between. the elements urges them apart maintains them normally in the positions described.

When the prongs of a plug are inserted into the modified receptacle to engage the cam surfaces ll of the door elements, they are first rocked along their lines of contact with projections (i -l, until the long leg Ell of each element may pass the end of the short leg 35% of the other element. The action of the prongs of the plug on the cam surfaces ll then forces the elements toward one another to permit the prongs to pass through the passages and into engagement with the receptacle terminals 23.

In both forms of the new receptacle, the safety means includes only three working parts, narnely, the two identical door elements 3 3 and the spring 39. The cost of producing the safety means is, therefore, relatively low and this is true also of the labor charges for assembling the safety means.

Receptacles of the type described are frequen 1y used in circuits, in which the currents flowing are such that the breaking of the connections by removal of the plug results in an arc, which ma extend from one of we terminals through 9 sage and out of the receptacle. In the new receptacle, the removal of the plug causes the door elements to close the passages immediately and this results in suppression of the are.

I claim:

1. In an electric receptacle having a pair of terminals and parallel passages, into which the c nnection prongs of a plug may be inserted to maize contact with the terminals, the comination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages a long leg and a short leg extending from one side of the base, the outer surfaces of the long and short legs of each element in a plane, the elements normally having 1 contact with one wall at opposite ends of bases and lying with the outer surfaces of their legs in contact with the other wall and with the long leg of each element aligned with the short leg of the other and with the ends of said legs opposed to each other, and a spring between the elements holding them in their normal positions.

2. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending from one side of the base, the outer surfaces of the long and short legs of each element lying in a plane, the elements normally engaging one wall over long narrow areas at op posite ends of their bases and extending in the same direction as the legs, the elements being rockable on such areas toward and away from that wall, the elements normally lying with the outer surfaces of their legs in contact with the other wall and lying with the long leg of each element aligned with the short leg of the other and with the ends of said legs opposed to each other, and a spring between the elements holding them in their normal positions.

3. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the Walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending from one side of the base, the outer surfaces of the long and short legs of each element lying in a plane, the elements normally having limited contact with the inner wall at opposite ends of their bases and lying with the outer surfaces of their legs in contact with the outer wall and with the long leg of each element aligned with the short leg of the other and with the ends of said legs opposed to each other, and a spring between the elements holding them in their normal positions.

4. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending from one side of the base, the outer surfaces of the long and short legs of each element lying in a plane, the elements normally engaging the inner wall over long narrow areas at opposite ends of their bases and extending in the same direction as the legs, the elements being rockable on such areas toward and away from that wall, the elements normally lying with the outer surfaces of their legs in contact with the outer wall and lying with the long leg of each element aligned with the short leg of the other and with the ends of said legs opposed to each other, and a spring between the elements holding them in their normal positions.

5. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending from one side of the base, the long legs being thinner than the short legs and the outer surfaces of the legs of an element lying substantially in a plane, the elements normally engaging the inner wall over small areas at opposite ends of their bases and being rockable on such areas toward and away from that wall, the outer surfaces of the legs of the elements normally engaging the outer wall with the long leg of each element aligned with the short leg of the other, and a spring between the elements urging them apart and resisting rocking of the elements from their normal positions.

6. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending in parallel relation from one side of the base at opposite ends thereof, the outer surfaces of the legs of each element lying substantially in a plane and the inner surface of each element being formed with a projection at one end of the base and extending parallel to the legs, the elements normally engaging the inner wall at the ends of their projections and being rockable thereon toward and away from that wall, the outer surfaces of the legs of each element normally engaging the outer Wall with the long leg of each element aligned with the short leg of the other, and a spring between the elements urging them apart and resisting rocking thereof on their projections from their normal positions.

'7. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending in parallel relation from one side of the base at opposite ends thereof, the inner and outer surfaces of the elements lying in substantially parallel planes and the inner wall being formed with offset projections along opposite edges normally engaged by the inner surfaces of the elements at the ends of their bases, the ele- ,ments being rockable 0n the projections toward and away from the inner wall and the outer surfaces of the elements normally engaging the outer wall with the long leg of each element aligned with the short leg of the other, and a spring between the elements urging them apart and resisting rocking thereof on said projections from their normal positions.

8. In an electric receptacle having a pair of terminals and parallel passages, into which the connection prongs of a plug may be inserted to make contact with the terminals, the combination of spaced inner and outer walls between the passages, a pair of door elements between the walls, each element including a base having a cam surface normally lying within and closing one of the passages and a long leg and a short leg extending in parallel relation from one side of the base at opposite ends thereof, each element normally engaging the inner wall over a small area at the end of the base, from which the long leg extends, and lying in extended contact with the outer wall, the elements normally lying with the long leg of each element aligned ?7 with the short leg of the other and being rockable on their areas of contact with the inner wall to permit the elements to approach one another with the long leg of each element overlapping the short leg of the other, and a spring engaging each element between its legs, the spring urging the elements apart and resisting rocking of the elements from their normal positions.

CHARLES T. VON HOLTZ.

REFERENCES CITED The following references are of record in "the file of this patent:

Number Number 3 UNITED STATES PATENTS Name Date Blinn Apr. 25, 1939 FOREIGN PATENTS Ceuntry Date Switzerland Apr. 1, 1931 England June 28, 1939 

